1. Field of the Invention
This invention relates to apparatus used to power flying vehicles such as aircraft, aerospacecraft, missiles and rockets. The improved engine apparatus provides a combination of ejector and ramjet elements to enable efficient engine performance over the velocity range of zero to hypersonic flight.
2. Description of Realted Art
There are currently disclosed in the literature many techniques for construction of ramjet engines and for use of injectors with ramjet engines to form an ejector to operate cooperatively with the ramjet cycle of the engine. However, no practical, operational ejector ramjet engine for engine operation from zero velocity to hypersonic flight appears to have been developed.
The ejector ramjet engine offers advantages relative to the conventional ramjet engine such as sea level static thrust and engine thrust at low level flight speeds. For a given flight condition the ejector ramjet can provide larger engine thrust than the conventional ramjet engine. This may be particularly advantageous during flight vehicle transonic acceleration and hypersonic flight conditions where ramjet thrust may not satisfy vehicle requirements. Improved combustor performance due to higher pressure and temperature levels in the combustor can also be achieved which allow combustor operation at higher flight altitudes than possible with a ramjet engine. The ejector ramjet also allows injection of excess oxidizer to enrich the oxidizer in combustion to further increase thrust.
Various methods for augmenting jet engines or ramjet engines have been proposed as typified by the disclosures in U.S. Pat. No. 5,129,227, granted Jul. 14, 1992 and U.S. Pat. No. 5,327,721, granted Jul. 12, 1994. In the case of U.S. Pat. No. 5,129,227, a fuel rich injectant is introduced into the mixing zone of a duct to form an ejector. The composition or equivalency ratio and the temperature of the injected gas is controlled to prevent combustion in the mixing duct. The velocity flow along the wall of the duct is also controlled by the structure of the injector to aid in preventing propagation upstream of the combustion from the combustor.
With regard to U.S. Pat. No. 5,327,721, a rather complex system to improve on the entrainment of fluid as disclosed in related art is presented. An injector is modulated to alternate the direction of the primary fluid jet in an ejector to entrain secondary fluid. The oscillation of the primary jet provides energy exchange between the primary and secondary fluids in the propulsion duct in a substantially non-viscous fashion.
Techniques for mixing fluids or hypermixing are exemplified by U.S. Pat. No. 4,257,224, granted Mar. 24, 1981 and in the article Journal of Aircraft, Vol. 9, No. 3, March 1972, Pgs. 243-248, by Richard B. Fancher, entitled "Low-Area Ratio, Thrust-Augmenting Ejectors". U.S. Pat. No. 4,257,224 presents a method and apparatus for improving the mixing of two fluids using an active element in the vicinity of the beginning of the mixing region. Oscillations are induced in the two fluids about an axis substantially normal to the mixing region flow axis.
The article by Fancher discusses various hypermixing techniques and includes the disclosure of an experimental ejector design and setup. The disclosed design uses a primary nozzle which is segmented into 24 elements 11/2 inches long. Each element gives its exiting mass a velocity component normal to both the nozzle's major axis and the fluid flow axis; the direction of this lateral velocity component was alternated from element to element.
The present invention uses a combination of a ramjet engine having: a movable plug in the exit nozzle; an injector assembly having slot nozzles with alternating orientation relative to the longitudinal axis or fluid flow axis of the engine and located at the upstream end of the mixing section; and provision to allow an external or internal, relative to the ramjet engine, combustion chamber to create the gas for the injector assembly. For the ejector ramjet engine to function with vehicles that operate over a velocity range of zero to hypersonic, a liquid air cycle process may be used with the injectors that uses the cooling properties of liquid hydrogen stored on the vehicle to liquefy environmental air as the oxidizer for the injector combustion chamber. By storing excess liquid air it can be used to augment the air flow received in the inlet when the altitude of the vehicle is such that the air flow received at the inlet is not of sufficient pressure to support combustion in the combustor.